Percussive drilling machine

ABSTRACT

The machine incorporates an air-operated striking piston whose body contains an air-distribution arrangement and a hammer reciprocating due to the action of compressed air so as to deliver at the end of a work stroke a blow at a drill steel arranged in the front part of the machine. Accommodated in the front part of the machine is a rotary impulse fronthead whose body contains an annular striking piston with projections and a rotary anvil with co-operative indentations and projections so arranged that their side surfaces and walls of the fronthead body form work stroke and idle stroke chambers which connect to a source of compressed air or atmosphere at regular intervals. The projections of the annular striking piston oscillate in these chambers back and forth and through an angle at a high rate due to the action of compressed air so as to deliver at the end of a work stroke a blow at the cooperative projections of the rotary anvil, causing to rotate the rotary anvil linked with the drill steel. Arranged in the front part of the fronthead body is a ratchet mechanism which assures that the rotary anvil and the drill steel rotate in only one direction.

United States Patent 1191 Bazhal et al.

[ Apr. 2, 1974 PERCUSSIVE DRILLING MACHINE [76] Inventors: AnatolyIgnatievich Bazhal, Ulitsa Franko, 30, kv. 42; Leonid PetzovichPonomozenro, Ulitsa 50 Let, Komsomola, l9, kv. 27, both of Zheltye VodyDnepropetrovskoi oblasti, U.S.S.R.

[22] Filed: Oct. 24, 1972 [21] Appl. No.: 300,240

52 us. c1. .Q 173/93, 173/108 51 Int. Cl 1125a 15/02, 1321b 1/12 58Field 01 Search 173/93, 93.5, 93.6, 104-108; 81/523 [56] ReferencesCited UNlTED STATES PATENTS 1,160,648 11/1915 Peck 173/108 2,108,9892/1938 Mack 173/108 X Primary ExaminerMarvin A. Champion AssistantExaminer-William F. Pate lIl Attorney, Agent, or Firml-1olman & Stern[57] ABSTRACT The machine incorporates an air-operated striking pistonwhose body contains an air-distribution arrangement and a hammerreciprocating due to the action of compressed air so as to deliver atthe end of a work stroke a blow at a drill steel arranged in the frontpart of the machine.

Accommodated in the front part of the machine is a rotary impulsefronthead whose body contains an annular striking piston withprojections and a rotary anvil with co-operative indentations andprojections so arranged that their side surfaces and walls of thefronthead body form work stroke and idle stroke chambers which connectto a source of compressed air or atmosphere at regular intervals. Theprojections of the annular striking piston oscillate in these chambersback and forth and through an angle at a high rate due to the action ofcompressed air so as to deliver at the end of a work stroke a blow atthe cooperative projections of the rotary anvil, causing to rotate therotary anvil linked with the drill steel. Arranged in the front part ofthe fronthead body is a ratchet mechanism which assures that the rotaryanvil and the drill steel rotate in only one direction.

5 Claims, 10 Drawing Figures PATENTEI] APR 2 I974 SHEET 1 (IF 4AIENTEUAPR 21914 8.800.888

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PERCUSSIVE DRILLING MACHINE BACKGROUND OF THE INVENTION The presentinvention relates to air-operated percussive drilling machines and, morespecifically, to percussive drilling machines with an independentnonreversible rotation of the drill steel for drilling holes.

PRIOR ART Known in the art is a percussive drilling machine with anindependent rotation of the drill steel comprising an air-operatedstriking rearhead consisting of a body with a cylindrical bore whichcontains an air-distribution arrangement and a hammer reciprocating dueto the action of compressed air so as to deliver, at the end of a workstroke, a blow at the drill steel arranged in the front part of saidmachine; a rotary impulse fronthead consisting of a body with acylindrical bore which contains at its rear end an annular strikingpiston with annular projections, a rotary anvil with co-operativeannular indentations and projections so arranged that their side surfaceand the wall of said rearhead body form, during each work and idlestroke, air chambers connecting via passages to a source of compressedair or atmosphere at regular intervals and providing for saidprojections of said annular striking piston space to oscillate both backand forth and through an angle at a high rate due to the action ofcompressed air so as to deliver at the end of a work stroke a blow atsaid cooperative projection of said rotary anvil and to cause the rotaryanvil to rotate integrally with the drill steel; and a ratchet mechanismarranged at the front end of a fronthead body.

In the known drilling machine, the ratchet mechanism comprises a ratchetring with internal teeth and an anvil incorporating pawls. The ratchetring has annular projections on its outside surface and striking againstthese projections are the annular projections of the annular strikingpiston as this oscillates both back and forth and through an angle.

The annular striking piston is arranged with its projections in the airchambers formed by the indentations and projections of a staticallyfixed stator and airdistribution sleeve. The passages which distributecompressed air are arranged so that the blows are of definite force andamplitude, providing thus for a certain performance of the machine.

The blows produced by mutualimpacts of the projections of the ratchetring with those of the annular striking piston are transmitted throughthe teeth of the ratchet ring and the pawls to the anvil, causing thisto turn through a certain angle. The anvil is connected by its end-facedetents to a drive sleeve and this, sleeve in its turn, is connected toa spindle holding the drill steel. Owing to this arrangement, the anviltends to turn the drill steel through a certain angle under the actionof blows.

However, the interaction of the spindle and drill steel with the rockbeing of a resilient nature, the torsional reaction resulting from thisinteraction tends to turn the spindle integrally with the components ofthe annular striking piston linked with it in the direction opposite tothat of the torque produced by the blow. Since the spindle with thedrive sleeve lacks any means of being locked in each of the changingpositions, the spindle is free to reverse from time to time if theresilient reaction due to the interaction of the drill steelrock systemexceeds the torque produced. This changes the amplitude of reciprocatingand angular oscillations of the annular striking piston, interferes withthe regular operation of the air-distribution system in the rotaryimpulse fronthead and brings the annular striking piston to a standstillor causes it to idle, i.e., to operate without striking against theprojections of the ratchet ring linked with the spindle throughintermediate components. As a result the spindle stops. Irregularrotation of the spindle with the drill steel impairs the effectivenessof the drilling operation.

Apart from the above, the known drilling machine is designed onsophisticated lines; its air-distribution mechanism is locatedseparately and the ratchet mechanism juxtaposed co-axially with theannular striking piston. This arrangement calls for a multitude ofcomponents to be incorporated into the air-distribution mechanism andthe mechanism linking the annular striking piston with the spindle. As aresult, the known machine is bulky and heavy.

OBJECTS AND SUMMARY OF THE INVENTION The object of the present inventionis to provide a machine which is capable of translating thereciprocating and angular oscillations of an annular striking pistonocurring at a high rate into practically ceaseless rotation of a rotaryanvil linked with the drill steel.

Another object of the present invention is to provide a machine which isless sophisticated, bulky and heavy.

These and other objects are accomplished in a percussive drillingmachine with independent nonreversible rotation of the drill steel whichcomprises an air-operated striking rearhead defined by a body providedwith a cylindrical bore which contains an airdistribution arrangementand a hammer reciprocating due to the action of compressed air so as todeliver at the end of a work stroke a blow at the drill steel arrangedin the front part of said machine; a rotary impulse fronthead defined bya body provided with a cylindrical bore which contains in its rear partan annular striking piston with projections located at the end oppositeto the drill steel and a rotary anvil with cooperative indentations andprojections so arranged that their side surfaces and walls of said rearrearhead body form, during each work and idle stroke, air chambersconnected via passages to a source of compressed air or atmosphere atregular intervals and providing for said projections of said annularstriking piston space to oscillate both back and forth and through anangle at a high rate due to the action of compressed air so as todeliver, at the end of a work stroke, a blow at said cooperativeprojections of said rotary anvil, causing to rotate said anvil and thedrill steel linked with the anvil by means of intermediate components;and a ratchet mechanism arranged at the front end of said frontheadbody. According to the invention, said ratchet mechanism is interposedbetween said rotary anvil and said fronthead body and comprises aratchet wheel linked up with said fronthead body and pawls located inthe end face of said rotary anvil facing the drill steel; said ratchetmechanism provides for the rotation of both the rotary anvil and drillsteel in only one direction.

A drilling machine arranged on the above lines allows to translate thereciprocating and angular oscillations of the annular striking pistonoccuring at a high rate into practically ceaseless rotation of therotary anvil with the drive sleeve and of the spindle with the drillsteel.

It is preferred to locate the annular striking piston inside acylindrical opening of the rotary anvil in order to facilitate a compactarrangement of air passages between working chambers, a source ofcompressed air and the atmosphere.

It is also preferred to provide in the outside surface of the rotoranvil, inlet and outlet passages and radial passages permanentlyconnected therewith and to provide in the annular striking piston,longitudinal passages on both sides of the projections by means of whichpassages and said radial passages the striking piston connects, duringits reciprocating and angular oscillation, the work and idle strokes airchambers to said radial inlet and outlet passages and, consequently, toa source of compressed air or the atmosphere at regular intervals.

Furthermore, it is preferred to arrange the radial inlet and outletpassages of the rotary anvil so that at least one inlet and one outletpassage is connected simultaneously and individually to one of the twolongitudinal passages opening into the work and idle strokes airchambers; such arrangement enhances the operational reliability of themachine at any speed of drilling or, in other words, provides for arotary impulse fronthead not sensitive to the changes in the resilientinteraction of the drill steel with the rock.

Finally is is preferred that the longitudinal passages of the strikingpiston be arranged symmetrically and have the same length which is notless than the distance between the end face of the annular strikingpiston opposite to the drill steel side and the edge of the annularinlet passage of the rotor anvil; this arrangement enables thelongitudinal passages of the annular striking piston to connect atregular intervals, when the annular striking piston and the rotary anvilare set rotating, with the radial passages of rotary anvil opening intothe annular inlet or outlet passage with the result that the drillingmachine is of less sophisticated design and is more compact.

The present invention will be best understood from the followingdescription of a preferred embodiment when read in conjunction with theaccompanying drawings, in which:

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram of adrilling rig for drilling holes underground with a percussive drillingmachine according to the invention;

FIG. 2 illustrates a percussive drilling machine according to theinvention in longitudinal section;

FIG. 3a and 3b is a section on line IIIIII of FIG. 2;

FIG. 4a and 4b is a section on line IV-IV of FIG. 3;

FIG. 5a and 5b is a section on line VV of FIG. 2; and

FIG. 6a and 6b is a section on line VIVI of FIG. 2.

DETAILED DESCRIPTION OF THE INVENTION FIG. 1 illustrates a rig fordrilling holes underground by means of a drilling machine according tothe invention which rig comprises a drilling machine proper 1,accommodating at the front end, a drill steel 2 provided with a bit 3 atthe tip, and a feed arrangement 4 imposing an axial feed load.

The drilling machine 1 and the feed arrangement 4 are located on acarriage 5 which serves to transport these components to the face andperform all manipulations associated with the setting of the machine andfeed arrangement for drilling holes.

Arrows A and B indicate the connections to the compressed air mains ofthe mine.

The percussive drilling machine 1 with an independent non-reversiblerotation of the drill steel shown in FIGS. 2 through 6 comprises anair-operated striking rearhead 6 and a rotary impulse fronthead 7.

The air-operated striking rearhead 6 has a body 8 with a cylindricalbore accommodating an airdistribution arrangement (the air-distributionand on/- off arrangements are not shown in the drawing and can be of anytype) and a movable hammer 9. The body 8 is linked with the impulsefronthead through the intermediary of an adapter sleeve 10.

The rotary impulse fronthead has a body 11 with a cylindrical borelimited by the end faces of the adapter sleeve 10 and an adapter sleeve12 located at the drill steel side.

Arranged at the front end of the body 11 there is a ratchet wheel 13with teeth 14 (FIG. 6a), with said ratched wheel being linked up withsaid body. The outside surface of the body 11 is provided with a port 11for admitting compressed air from a source into the rotary fronthead andwith ports 16 for releasing compressed air into the atmosphere.

Located in the cylindrical bore of the fronthead body 11 are a rotaryanvil 17 and an annular striking piston 18, both capable of rotating.The rotary anvil 17 is a cylindrical sleeve with a stepped bore andannular indentations 19 located next to annular projections 20 (FIGS.3a; b) at the end opposite to the drill steel.

In the outside surface of the rotary anvil 17 are provided annularair-distribution passages, an inlet passage 21 permanently connected tothe compressed air inlet port 15 and an outlet passage 22 permanentlyconnected to the compressed air outlet ports 16 (FIG. 2).

The inlet passage 21 communicates with radial passages 23 and 24 whereasthe outlet passage 22 connects with radial passages 25 and 26 of therotary anvil 17 (FIGS. 5a; b).

The annular striking piston 18 (FIGS. 3a; b) is a cylindrical sleevewith annular projections 27 which is arranged so as to be capable ofrotating in the bore of the rotary anvil 17 at the side opposite to thedrilling steel 2. Extending symmetrically on both sides of theprojections 27 of the annular striking piston 18 are longitudinalpassages 28 and 29. The projections of the annular striking piston arearranged in co-operative indentations 19 of the rotary anvil whoseprojections 20 limit the angular travel of the projections 27. Theprojections 27 of the annular striking piston I8 divide the space of theindentations I9 in the rotary anvil 17 into work stroke chambers 30 andidle stroke chambers 31. (The number of chambers varies with thespecified rating of the rotary fronthead and is governed by the overalldimensions of the machine). The longitudinal passages 28 and 29 placingthe chambers 30 and 31 in communication with either the inlet passages23 and 24 or the outlet passages 25 and 26 are of the same length toprovide for said connection of the work stroke chambers 30 and the idlestroke chambers 31 either to the radial inlet passages 23 and 24 or tothe radial outlet passages 25 and 26.

The volume of the work and idle chambers is a variable one. When theannular striking piston abuts against the air cushions in the workstroke chambers 30 as shown in FIG. 3a, the volume of the work strokechambers is at its minimum and that of the idle stroke chambers 31 is atits maximum.

When the projections 27 of the annular striking piston 18 deliver a blowat the projections of the rotary anvil 17, as shown in FIG. 3b, thevolume of the work stroke chambers is at its maximum and that of theidle stroke chambers 31 is at its minimum. Each of the chambers 30 and31 can communicate with either the annular inlet passage 21 or theannular outlet passage 22.

The work stroke chambers 30 can be connected either to the inlet passage21 via the longitudinal passages 28 and the radial passages 23 or to theoutlet passage 22 via the same longitudinal passages 28 and the radialpassages 25.

The idle stroke chambers 31 can be connected either to the outletpassage 22 via the longitudinal passages 29 and the radial passages 26or to the inlet passage 21 via the same longitudinal passages 29 and theradial passages 24.

The chambers 30 and 31 have sealing arrangements in the form of vanes 33acted upon by springs 32 and arranged in the projections 20 of therotary anvil 16 and in the annular striking piston 18.

Arranged in the end face of the rotary anvil I7 at its end facing thedrill steel are spring loaded pawls 34 (FIGS. 6a; b; the springs are notshown in the drawing for the sake of simplicity) and end-face detents(FIG. 2). The pawls 34 permanently engage teeth 14 of the fronthead body11 so as to lock the rotary anvil 17 in each of its positions.

The rotary anvil 17 is connected by means of the endface detents 35 to adrive sleeve 36 (FIG. 2) installed in a cover plate 37. Arranged insidethe drive sleeve 36 is a spindle 38 accommodating the drill steel 2 bymeans of a threaded or tapered hole.

The drilling machine operates on the following lines, the originalposition is the one shown in FIGS. 3a, 4a, 5a and 6a when the annularstriking piston 18 has been brought to a halt due to the braking effectof the air cushions in the work stroke chambers 30. As soon as thedrilling machine is activated, compressed air from a source of supply isadmitted through the connections indicated by arrows A and B (FIG. 2)into the airdistribution arrangement of the air-operated strikingrearhead 6 (arrow A) and into the inlet port 15 of the rotary impulsefronthead 7 (arrow B).

Under the effect of compressed air which has entered the strikingrearhead 6, the hammer 9 travels back and forth, delivering at the endof each work stroke a blow at the spindle 38 holding the drill steel 2with the bit 3.

When compressed air is admitted through the port 15 into the rotaryimpulse fronthead 7, it flows through the annular inlet passage 21, theradial inlet passage 23 of the rotary anvil 17 and then through thelongitudinal passaged 28 of the annular striking piston 18 into the workstroke chambers 30 (FIGS. 3a; 4a and 5a).

At the same time, the idle stroke chambers 31 are connected through thelongitudinal passages of the annular striking piston 18 to the outlets,the radial passages 26 and the annular passage 22, of the rotary anvil17 or, in other words, to the atmosphere.

While the idle stroke chambers 31 are connected to the atmosphere, thepressure in such chambers is close to atmospheric. In the work strokechambers 30 the pressure rapidly builds up and the difference inpressure between the chambers 30 and 31 causes the annular projections27 of the annular striking piston 18 to turn towards the projections 20of the rotary anvil 17 (this is the work stroke). As the annularstriking piston 18 moves further, the longitudinal passages 28 aredisconnected from the radial inlet passages 23 of the rotary anvil 17and the flow of compressed air into the work stroke chambers 30 is cutoff. Further movement ofthe annular striking piston 18 takes place dueto the expansion of the compressed air admitted into the chambers 30.

At the same time, the idle stroke chambers 31, so far connected via thelongitudinal passages 29 of the annular striking piston 18 to the radialoutlet passages 26 of the rotary anvil 14, become disconnected fromthese passages and the annular outlet passage 22 or, in other words,from the atmosphere.

As the annular striking piston 18 continues its movement, thelongitudinal passages 28 are placed into communication with the radialoutlet passages of the rotary anvil 17 and the work stroke chambers 30are connected to the atmosphere.

When compressed air has escaped from the work chambers 30, the annularstriking piston 18 continues its movement due to inertia, admitting anew charge of compressed air into the idle stroke chambers 31 throughthe longitudinal passages 29, radial inlet passages 24 and annular inletpassage 21. At the same time, the projections 27 of the annular strikingpiston 18 continuing its rotation due to inertia strike at theprojections 20 of the rotary anvil 17 causing said anvil to turn throughan angle a as shown by arrows in FIGS. 3b and 6b).

On delivering the blow, the annular striking piston 18 turns integrallywith the rotary anvil 17 until a pressure build up in the idle strokechambers 31 and, to a certain extent, the recoil of the annular strikingpiston projections 27 from the rotary anvil projections 20 will reversethe annular striking piston 18 so that it turns away from the rotaryanvil projections.

On its back stroke which is the idle one, the annular striking piston 18disconnects the longitudinal passages 29 from the radial inlet passages24 and also disconnects the idle stroke chambers 31 from the radialinlet passage 21 of the rotary anvil 17. At the same time, the annularstriking piston 18 disconnects the longitudinal passages 28 from theradial outlet passages 25 and, consequently, disconnects the work strokechambers 30 from atmosphere.

Continuing its rotation in the same direction, the annular strikingpiston 18 connects the idle stroke chambers 31 to atmosphere via itslongitudinal passages 29, the radial outlet passages 26 and the annularoutlet passage 22 of the rotary anvil 17 and also connects the workstroke chambers 30 to a source of compressed air through thelongitudinal passages 28, the radial inlet passages 23 and the annularinlet passage 21 of the rotary anvil 17. On turning still further, thestriking piston is braked and brought to a halt by the air cushionsformed in the work stroke chambers 30. The pressure in these work strokechambers sharply increases and the difference in pressure acting on theprojections 27 in the work stroke and idle stroke chambers 30 and 31,

respectively, causes the annular striking piston 18 to start turningtowards the projections 20 of the rotary anvil 17, beginning thus thework stroke. The cycle is repeated.

To assure that the work stroke chambers 30 and the idle stroke chambers31 are reliably connected either to atmosphere or to a source ofcompressed air without the danger of dead centers, the radial inletpassages 23 and 24 and also the radial outlet passages 25 and 26 of therotary anvil 17 are offset with respect to the symmetrically arrangedlongitudinal passages 28 and 29 of the annular striking piston by anamount which enables at least one of the radial inlet passages 23 and 24to connect the chambers 30 and 31 either to atmosphere by way of theannular outlet passage 22 or to a source of compressed air through theannular inlet passage 21 of the rotary anvil 17.

The work and idle strokes described above follow in a rapid succesion sothat the torque impulses produced by the interaction of the projections27 of the annular striking piston 18 with the projections 20 of therotary anvil I7 cause said anvil to rotate at regular intervals; thisrotation is transmitted through the end-face detents 35 to the drivesleeve 36 and the spindle 38 with the drill steel 2.

When the rotary anvil 17 oscillates both back and forth and through anangle a the spring-loaded pawls 34 (FIG. 6a) secured to the anvil slipresiliently over teeth 14 of the fronthead body 11 and, on displacingthrough the same angle, lock the rotary anvil and all components linkedtherewith (the drive sleeve 36, the spindle 38 and the drill steel 2) ineach new position. The pawls 34 prevent these components from reversingdue to the resilient reaction of the drill steel under the torsionalforces coming into play while the rock is being drilled and since thetorque blows at the rotary anvil are produced at a rapid rate said anvilrotates practically ceaselessly and in only one direction integrallywith the drive sleeve 36, the spindle 38 and the drill steel 2.

What is claimed is:

1. A percussive drilling machine with independent rotation of a drillsteel arranged in a front part thereof comprising an air-operatedstriking rearhead including a body provided with a cylindrical bore, anairdistribution arrangement and a hammer contained in the cylindricalbore of said body; said hammer reciprocates due to the action ofcompressed air so as to deliver at the end of a work stroke a blow atthe drill steel; said rotary impulse fronthead including a body providedwith a cylindrical bore; an annular striking piston with projections anda rotary anvil with co-operative indentations and projections, saidpiston and said anvil being contained in the bore of said rotary impulsefronthead; work stroke air chambers and idle stroke air chambers definedby side surfaces of said projections of the annular striking piston androtary anvil and also by walls of the body of said rotary impulsefronthead, said chambers connecting via passages to a source ofcompressed air or atmosphere at regular intervals; said projections ofthe annular striking piston being arranged inside said work stroke airchambers in which these projections oscillate back and forth and throughan angle at a high rate due to the action of compressed air so todeliver at the end of a work stroke a blow at said co-operativeprojections of the rotary anvil linked with the drill steel throughintermediate components and to cause the drill steel to rotate; aratchet mechanism arranged at a front end of said fronthead body betweensaid rotary anvil and said fronthead body, said ratchet mechanismcomprising a ratchet wheel linked with said fronthead body andspring-loaded pawls located in an end face of said rotary anvil facingthe drill steel and permanently engaged with teeth of said ratchet wheelso as to lock said rotary anvil in each position and assure that therotary anvil and, consequently, the drill steel rotate in only onedirection.

2. The drilling machine according to claim 1 in which said annularstriking piston is located inside said rotary anvil.

3. The drilling machine according to claim 1 in which said rotary anvilhas in its outside surface an annular inlet passage and an annularoutlet passage and also radial passages and permanently connected tosaid inlet and outlet passages, respectively, whereas said annularstriking piston has longitudinal passages on both sides of itsprojections by means of which passages and said radial passages and saidstriking piston connects during its reciprocating and angularoscillations said work stroke chambers and idle stroke chambers to saidannular inlet passage and said annular outlet passage and, consequently,to a source of ccimpressed air or atmosphere at regular intervals.

4. The drilling machine according to claim 3 in which the radial inletpassages and the radial outlet passages of the rotary anvil are arrangedso that at least one of the inlet passages and one of the outletpassages are connected simultaneously and individually to one of the twolongitudinal passages opening into the work stroke chambers and idlestroke chambers.

5. The drilling machine according to claim 3 in which the longitudinalpassages of the annular striking piston are arranged symmetrically andhave the same length which is not less that the distance between the endface of the annular striking piston opposite the side at which the drillsteel is located and the edge of the annular inlet passage of the rotaryanvil enabling the longitudinal passages to connect at regularintervals, when the annular striking piston and the rotary anvil are setrotating, with the radial passages of the rotary anvil opening into theannular inlet passage or the annular outlet passage.

1. A percussive drilling machine with independent rotation of a drillsteel arranged in a front part thereof comprising an airoperatedstriking rearhead including a body provided with a cylindrical bore, anair-distribution arrangement and a hammer contained in the cylindricalbore of said body; said hammer reciprocates due to the action ofcompressed air so as to deliver at the end of a work stroke a blow atthe drill steel; said rotary impulse fronthead including a body providedwith a cylindrical bore; an annular striking piston with projections anda rotary anvil with co-operative indentations and projections, saidpiston and said anvil being contained in the bore of said rotary impulsefronthead; work stroke air chambers and idle stroke air chambers definedby side surfaces of said projections of the annular striking piston androtary anvil and also by walls of the body of said rotary impulsefronthead, said chambers connecting via passages to a source ofcompressed air or atmosphere at regular intervals; said projections ofthe annular striking piston being arranged inside said work stroke airchambers in which these projections oscillate back and forth and throughan angle at a high rate due to the action of compressed air so todeliver at the end of a work stroke a blow at said cooperativeprojections of the rotary anvil linked with the drill steel throughintermediate components and to cause the drill steel to rotate; aratchet mechanism arranged at a front end of said fronthead body betweensaid rotary anvil and said fronthead body, said ratchet mechanismcomprising a ratchet wheel linked with said fronthead body andspring-loaded pawls located in an end face of said rotary anvil facingthe drill steel and permanently engaged with teeth of said ratchet wheelso as to lock said rotary anvil in each position and assure that therotary anvil and, consequently, the drill steel rotate in only onedirection.
 2. The drilling machine according to claim 1 in which saidannular striking piston is located inside said rotary anvil.
 3. Thedrilling machine according to claim 1 in which said rotary anvil has inits outside surface an annular inlet passage and an annular outletpassage and also radial passages and permanently connected to said inletand outlet passages, respectively, whereas said annular striking pistonhas longitudinal passages on both sides of its projections by means ofwhich passages and said radial passages and said striking pistonconnects during its reciprocating and angular oscillations said workstroke chambers and idle stroke chambers to said annular inlet passageand said annular outlet passage and, consequently, to a source ofcompressed air or atmosphere at regular intervals.
 4. The drillingmachine according to claim 3 in which the radial inlet passages and theradial outlet passages of the rotary anvil are arranged so that at leastone of the inlet passages and one of the outlet passages are connectedsimultaneously and individually to one of the two longitudinal passagesopening into the work stroke chambers and idle stroke chambers.
 5. Thedrilling machine according to claim 3 in which the longitudinal passagesof the annular striking piston are arranged symmetrically and have thesame length which is not less that the distance between the end face ofthe annular striking piston opposite the side at which the drill steelis located and the edge of the annular inlet passage of the rotary anvilenabling the longitudinal passages to connect at regular intervals, whenthe annular striking piston and the rotary anvil are set rotating, withthe radial passages of the rotary anvil opening into the annular inletpassage or the annular outlet passage.